Resistor spool



July 22, 1952 w, HULL 2,604,275

RESISTOR SPOOL Filed Sept. 28, 1946 INVENTOR. RICHARD W HULL avib [@77 0NEW Patented July 22, l952 RESISTOR SPOOL Richard W. Hull, Pasadena;Calif., assignonto Consolidated Engineering Corporation, Pasadena,Calif., a corporation of California Application September 28, 1946,Serial No. 699,982

'1 This invention relates to electrical coil devices of the type woundcnspools such as inductances and resistances.

The principal object is to provide a spool construction for suchwire-wound structures as will minimize the likelihood of damage tothewire coil and its insulation.

It is a commonpractice to wind coils of insulated wire on a spool toprovide inductance or resistance elements. In the case of resistanceelements, it isoften desired to make them of the non-inductive type, andthis requires reversal of the direction ofwinding at relatively shortintervals, according "to a well-known practice. The reversals ofdirection are frequently performed by the provision-of a spool having anumber of winding spaces or sections arranged around the longitudinalaxis of the spool; and slots are cut in the partitions between thesections to enable the wire to be carried through from one section tothe next. Itordinarily happens that when the wire is carried through aslot from one spool section to the next, it will be carried down aroundthe inside circumference of the spool, so that subsequent layers of thewire will be wound around and rub alongthe strand which has first beencarried down. This will frequently wearofi the insulation from thestrand and sometimes produces short circuits.

In accordance withmy invention, I provide a spool construction whichminimizes the undesired scraping-and wearing off of the Wire insulation.

- I carry out my invention by the provision of a spool having throughits end member and/or partitions a slot which is off center, that is,extends along a segment of the spool section rather than through itscenter. g

A feature of my invention is theprovision of a pair of slots at thepartition, and preferably the slots are tangentialto the core of thespool. According to one embodiment, for example, the slots are parallelto each other and'on either side of the center line. According toanother embodiment, th slots are non-parallel and converge toward eachother.

When the wire is carried through such slots, the wire comes downapproximately tangential to the core of the spool 50 that subsequentturns of the wire do not rub against the original strand which has beencarried through, and this minimizes the tendency toward damage totheinsulation. 1 i

The foregoing and other features of my invention will be betterunderstood from thel'following detailed description. andthe accompanyingdrawings of which: I

hold the insulated wire winding. spool partitions 4 is in the form of amember 1 Claim. (01142 -113) Fig. '1 is a side view of a. spoolinaccordance with my invention; I i- Fig. 2is an end view of the spool;Fig. 3 is an enlarged view showing partoi the spoolwith windingsrepresented on it; Fig. 4 is a cross-section view taken at line tlofFigpS; v

Fig. 5: is another enlarged view of. part of the spool showing adifierent arrangement of windings on'it;

Fig. 6 is a cross-section view taken at line 6-4; ofFig. 5;

Fig. '7 is a side view of a modification accordillg to my invention; and

. Fig.8 is a cross-section view taken at line 8.3 of Fig. 7. 1

Referring to Fig: l, the spool l comprises a pair of circular endmembers 2 and 3 between which arelocatedanumber ofpartitions d at spacedintervals apart, dividing the spool'into a number of winding-sections 5..The spool may be of. any suitable material, for example bake lite or arubber composition which will serve to Each of the having conical sidestapering to a narrower thickness at the outside, as shown in Fig. .1',so that each spool is provided with a central core 8 and outwardlytapering sides, this configuration being well adapted to receive a wirewinding.

It is desired that a single continuous winding be carried from ,onespool section ,to another, and for this purpose each partition isprovided with a pair of slots l and 8, the slots bein paralleLto eachother and extending from the circumference of the partition-to the core6 of .the spool. The slots are not arranged along a; d1? ameter oi thepartition, but instead, are arranged alonga line forming a segment ofthe partition, and are spaced so that the direction of the slot issubstantiallytangential to the circular corefi where the slots meet thecore. This arrangement is illustrated in Fig. 2;

To form a coil for a resistor winding, an insulated wirewill be Wound inthe sections 5' of the spool. Fig. 3'showssuch a winding, which is woundas a non-inductiveKresistance. The windingis formed byanv insulated wire9 which may be a well known type or covered wiresuch as an enamel-coatedwire. The windingis started by inserting the wire into the slot l of theend, piece -2, where .it will be suitably fastened or attached toaterminal memben. This'attachmentismade in the embodiment illustrated-bythe provision of a terminal wire .lil whichr-is in sorted in aperipheral groove ll around terminal piece 2, the wire In being suitablytwisted at l2 to hold a loop of the terminal wire tightly in the groovewhile allowing a convenient length of the terminal portion to protrudefrom the spool. The insulation will be scraped from wire 9 where itmeets terminal wire I at groove H of the end piece, and it may be loopedover the wire In and fastened by solder l3.

The wire 9 from the slot 1 is carried down into the winding section andwound on the spool in a counterclockwise direction (as viewed from theleft end of the spool in Fig. 3) until a sufileient amount of thewinding has been put into the section. Then the outermost strand of thewinding is carried through the slot 8 of the first partition membernearest the end member 2, and the wire is brought down to thecylindrical base of the spool in the second section, and the winding isformed in the second section in the clockwise direction, that is,opposite to the direction of winding in the first section.

In passing through the next partition, the wire will be brought throughthe slot 8 on the other side of the axis of the spool, and the windingin the following section will be reversed, that is, woundcounterclockwise like in the first section. In this way, the wire isbrought through successive partitions through the alternate slots 1 and8, and the windings in the successive sections are alternately clockwiseand counterclockwise. It will be recognized that this change ofdirection of the winding will create a substantially noninductive typeof resistance. At the end member 3, the end of the winding may beconnected to a terminal wire such as the wire I5 which may be attachedsimilarly to the attachment of terminal wire Hi.

It may. under some circumstances, be desired to wind all of the sectionsof the spool in the same direction. This can be done just as well aswinding them in opposite directions as in Fig. 3. Fig. 5 shows anarrangement in which the sections are wound in the same direction. InFig. 5, the

winding is carried down from the terminal wire [0 and wound in aclockwise direction in the first section of the spool, in a mannersimilar to the winding in the first section of Fig. 3. Then when thefirst section has received its full winding, the wire instead of beingbrought down through the opposite slot 1 is carried through slot 8 ofthe first partition; and in starting the winding in the second section,its direction is continued in the clockwise direction. The wire iscarried through all subsequent partitions through the slot 8 on the sameside of the axis of the spool, and the windings are all in the samedirection.

The tapered shape of the spool partitions 4 is especially advantageouswhen shrinkable material for the spool is used. Bakelite and some otherspool materials, for example, shrink with age so that the length of thespool tends to decrease somewhat. This has the effect of tending tocompress and squeeze the windings in the sections. By reason of thetapered sides to the partitions, however, the winding is enabled to besqueezed outwardly somewhat if and when such shrinkage occurs, withoutthe attendant danger of damage to the winding and its insulation if noroom for squeezing out were permitted.

Another modification of a spool made according to my invention isillustrated in Figs. 7 and 8. In this embodiment there is provided thecentral cylindrical core IS with its two end members l1 and I8 andpartitions l9 separating the spool into sections. The end members andthe partitions diiier somewhat from those in Figs. 1 to 6, in that theydo not taper toward the core of the spool, but instead, are in planesperpendicular to the longitudinal axis of the core. The slots 20 and. 2|through the end sections and partitions, instead of being parallel toeach other as in the preceding embodiments, are at an angle to eachother as shown in Fig. 8. In Fig. 8, the angle between slots 28 and 2|is shown as being substantially although it will be understood that someother angle might be used instead if desired. The slots, although at anangle to each other are arranged to be substantially tangential to thecore where they meet the core.

Except for the difference in angularity of the slots, and other detailssuch as the taper of the partitions, the windings in the spool may bemade the same as the embodiments in Figs. 1 to 6, and the windings maybe made the same way. The construction of Figs. '7 and 8 may haveadvantages over that of Figs. 1 to 6 in specific instances, for example,where the spool material is more brittle than is being used in theembodiments of Figs. 1 to 6. Where a brittle material is bein used, forexample a ceramic or the like, it may be undesirable to space the slotsclose together and parallel to each other as in Figs. 1 to 6, andinstead to space them somewhat further apart as shown in Figs. 7 and 8,to provide additional strength. Moreover, it may in some instances beundesirable to use tapered partition sections as shown in Figs. 1 to 6,and instead to use the straight-sided sections as shown in Figs. '7 and8.

When straight-sided partitions are used such as is shown in Fig. 7, aspool material will usually be selected which does not shrinkappreciably with age. A ceramic or porcelain material, for example, doesnot shrink much, and the coefficient of expansion of a ceramicis usuallyeven less than that of the wire.

By my novel forms of spool provided with slots arranged accordin to myinvention, it will be recognized that I have provided means whereby thewindings in a spool may be made without such serious risk of injury tothe insulation on the wire as if only a single centrally located slotwere used, as has heretofore been the practice. By carrying theinitiallead of a spool section down through the slot which is substantiallytangential to the inner cylindrical core of the spool on which thewinding is to be carried, there is very little scraping of subsequentlays of the winding over the initial wire which is carried through.

It will be recognized that if a single slot were used and the wirecarried down through the single slot, it would be bent in direction atthe position where the slot meets the spool; that is, it will turn atalmost a right angle in the direction of the tangent to the spoolcylinder at the base of the slot. This will result in the subsequentturns of the wire striking the right angle bend and scraping theinsulation ofi. If it should happen that the insulation should similarlybe scraped off one of the subsequent turns, there would be a resultingshort circuit of the turns.

By using the slot which is substantially tangential to the spool, inaccordance with my invention, there will be no bend of the Wire at thepoint where the slot lets the entrance wireinto the base of the spool,and accordingly less likelihood of damage to the insulation.

It will be recognized that my invention is not limited to the particularembodiments shown in the drawing, which are given for illustrationpurposes rather than for purposes of limitation. Other modificationswithin the scope of my invention will suggest themselves to thoseskilled in the art. For example, the advantage of my invention will beobtained even though the spool has only a single section for winding. Insuch a case, the advantage will be had on the carrying down of theinitial length or strand of wire from the terminal position to the baseof the spool.

I claim:

A spool having a core for holding an electrical winding comprising asection in which the winding is placed and a boundary wall at each end01! the section, at least one of the boundary walls having a pair ofslots oiI center with reference to the plane which passes through thelongitudinal axis of the spool and extending from the periphery of thepartition to the core of the spool for passage of the lead in wire tothe section, said slots being at substantially a ninety degree anglewith respect to each other and lying in planes which are substantiallytangential to the core of the spool where the slot meets the core.

RICHARD W. HULL.

REFERENCES CITED "I he following references are of record in the file o!this patent:

UNITED STATES PATENTS

